Various manually driven carrier vehicles, for example, hand trucks, carts and strollers, are commonly used for moving objects that are otherwise inconvenient for a person to carry due to size and/or weight, or for transporting infants and toddlers. Often, these carts and strollers have foldable chassis for ease of storage and transportation when not in use. These carriers typically have a telescoping or folding handle, a folding chassis, and wheels set into a predetermined position. Such carts and strollers often have limited capability to traverse rough or uneven terrain because the portability requirement in the folded state limits the range of possible wheel diameters, which, in turn, limits suspension responsiveness. This is because the efforts of moving a cart or a stroller at a given coefficient of friction depend inversely on ratios of wheel to axle diameters and the wheel diameter to height of an obstacle. Other carriers, besides having a telescoping or folding handle and a folding chassis, utilize removable wheels of relatively large size as means to improve terrain trafficability, yet reduce overall dimensions in the folded state. However, removing the wheels requires additional time and complicates handling and storage of the carrier, particularly after use on wet or muddy surfaces.
Thus, conventional folding carts and strollers, in addition to be able to transport a predetermined load, are designed primarily for convenient handling and portability when folded. However, these known carts and strollers, independently of any trade-offs between the convenience of use and the size in the folded state, are difficult to handle when moving over an irregular terrain, curbs, stairs, and other obstacles. Carrier chassis better capable of dealing with uneven surfaces are inconvenient to store or transport when folded.
Therefore, it is desirable to provide a folding carrier chassis capable of moving over a rough terrain, including curbs, stairs, and spongy soil. Additionally, it is desirable to have such carrier chassis be foldable relatively flat to provide for ease of storage and transportation. Further, such chassis should preferably be easily folded without disassembling.